11.1.1 Describe friction welding.
Friction welding is a completely mechanical solid-phase process in which heat generated by friction is used to create the ideal conditions for a high-integrity welded joint between similar or dissimilar metals.
11.1.2 Explain how two metal parts are welded using friction.
Diagrams should include two parts, one revolving, and the other fixed.
11.1.3 Describe plastic welding.
Consider hot air and friction welding techniques.
Below video on hot air welding
11.1.4 Explain how two plastic parts are welded together.
Only thermoplastics that do not burn or decompose when heated to their softening temperature can be welded.
11.1.5 Define permanent joining techniques.
Permanent joining techniques A permanent join is a type of fastening that is not supposed to be removed. It is only possible to remove such joins by drilling, cutting or grinding the join away.
11.1.6 List a range of permanent joining techniques.
Consider pop-rivets, brazing, welding and adhesives.
11.1.7 Discuss how permanent joining techniques lead to planned obsolescence and environmental issues.
Permanent joins do not allow for the disassembly and easy maintenance of products.
11.1.8 Define adhesive.
Adhesive An adhesive is a substance that is applied between two surfaces in order to bond them together.
11.1.9 Identify a range of adhesives suitable for joining metals, woods and plastics.
PVA (polyvinyl acetate), epoxy resin, contact adhesive, cascamite, tensol cement and superglue (cyanoacrylate).
PVA (polyvinyl acetate), epoxy resin, contact adhesive (applying laminates),cascamite,
Epoxy resin, superglue (cyanoacrylate)
Epoxy resin (some plastics), contact adhesive (neoprene), tensol cement, superglue (cyanoacrylate)
PVA - Elmers
11.1.10 Discuss the advantages and disadvantages of using adhesive bonding in products.
Consider preparation of surfaces, clamping, bonding time, type of material, and health and safety.
Preparation of surfaces
* No drilling of holes, etc
* Surface must be carefully cleaned
* Join all shapes and thicknesses * Provide smooth contours
* Jigs and fixtures may be needed * Heat and pressure may be required
* Long curing time allows for repositioning (Disadvantage as well)
* Long cure times may be needed
Type of material
* Join all shapes and thicknesses * Dissimilar materials can be bonded
* Certain adhesives are needed for the type of material.
Health and safety
* Fumes can be toxic * Human tissue can be bonded
Adhesives present several distinct advantages over conventional methods of bonding:
Provide large stress-bearing area
Provide excellent fatigue strength
Dampen vibration and absorb shock
Minimize or prevent galvanic corrosion between dissimilar metals
Join all shapes and thicknesses
Provide smooth contours
Join any combination of similar or dissimilar materials
Often less expensive and faster than mechanical fastening (can be automated)
Heat, if required, is too low to affect metals parts
Provide attractive strength-to-weight ratio.
However, there are also disadvantages which may make adhesive bonding impractical:
Surface must be carefully cleaned
Long cure times may be needed
Limitation on upper continuous operating temperature
Heat and pressure may be required
Jigs and fixtures may be needed
Rigid process control usually necessary
Inspection of finished joint difficult - Non distinctive testing not always possible
Useful life depends on environment
Special training is often required.
Bulleted list and italicised paragraphs are excerpted from Design Technology: guide. Cardiff Wales, UK: International Baccalaureate Organization, 2007.
Images are clickable links to its location.